Canon CP660 Service Manual page 180

CHAPTER 5 PICK-UP/FEEDING SYSTEM
2. Multifeeder Last Sheet Detection
The printer unit is capable of detecting the last sheet from the multifeeder. The feed-
ing distance from the multifeeder tray paper sensor to the registration roller is short; as
such, if the last sheet was picked up during continuous printing, writing would start before
the DC controller PCB identifies the absence of paper, requiring the printer unit to detect
the absence of paper before writing starts and, ultimately, to prevent soiling between the
photosensitive drum and the intermediate transfer drum.
The last sheet is detected by monitoring the rotation of the last sheet detecting roll
mounted to the multifeeder tray by the multifeeder tray last sheet sensor (P19).
If two or more sheets of paper exist on the multifeeder tray, the last paper detecting
roll will not rotate during pick-up operation. When the last sheet is picked up, however, the
sheet will rotate the last sheet detecting roll, causing the output of the last paper sensor
to change between '1' and '0'. In response, the DC controller PCB will assume that the
last sheet has been picked up, and communicate the fact (absence of paper) to the print-
1
er board* to stop writing the next image.
1
* Reader controller PCB (when making prints with the reader unit installed).
Multifeeder pick-up roller
5-18
COPYRIGHT © 1999 CANON INC.
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Multifeeder tray last paper sensor (PS19)
Last sheet detecting roll
Figure 5-214
CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
Last sheet